This invention relates to a semiconductor device having a bi-polar transistor structure which serves functions of photo-electric conversion, amplification, switching, memory, oscillation, negative resistance and electric current or voltage generation, for example, and is adapted for high integration, and more particularly, to a semiconductor device comprising a semiconductor region, an opposed region and a thin film which is interposed between the semiconductor region and the opposed region and has a wider forbidden band gap than that of the semiconductor region so as to form an electronic barrier at the interface between itself and the semiconductor region and a thickness small enough for the carriers to be transported by direct tunneling, Fowler-Nordheim tunneling, trap-assisted tunneling or the like (the various conduction mechanisms mentioned will be collectively referred to hereinafter as "tunneling" for simplicity of description) so as to permit the carriers to be injected from the opposed region across the thin film into the semiconductor region and through a depletion or inversion layer formed in the surface portion of the aforesaid semiconductor region and to reach the semiconductor region and/or form electron-hole pairs in the semiconductor region around the surface thereof.
Generally in the p-n junction type semiconductor devices, efficient injection of the carriers from one to the other region is not obtained unless each of the semiconductor regions forming the junction is made of a single crystal not appreciably abounding with defects or traps and the impurity density in the region accepting the carriers is lower by at least one order of magnitude than that in the other region. For this reason, in the design of semiconductor devices, the parasitic resistance and capacitance of devices have been restricted to a point where optimum design is hardly feasible.